Scar Extension Measured by Magnetic Resonance–Based Signal Intensity Mapping Predicts Ventricular Tachycardia Recurrence After Substrate Ablation in Patients With Previous Myocardial Infarction

Abstract Objectives The aim of this study was to determine if noninvasive measurement of scar by contrast-enhanced magnetic resonance imaging (MRI)–based signal intensity (SI) mapping predicts ventricular tachycardia (VT) recurrence after endocardial ablation. Background Scar extension on voltage mapping predicts VT recurrence after ablation procedures. Methods A total of 46 consecutive patients with previous myocardial infarction (87% men, mean age 68 ± 9 years, mean left ventricular ejection fraction 36 ± 10%) who underwent VT substrate ablation before the implantation of a cardioverter-defibrillator were included. Before ablation, contrast-enhanced MRI was performed, and areas of endocardial and epicardial scarring and heterogeneous tissue were measured; averaged subendocardial and subepicardial signal intensities were projected onto 3-dimensional endocardial and epicardial shells in which dense scar, heterogeneous tissue, and normal tissue were differentiated. Results During a mean follow-up period of 32 ± 24 months 17 patients (37%) had VT recurrence. Patients with recurrence had larger scar and heterogeneous tissue areas on SI maps in both endocardium (81 ± 27 cm2 vs. 48 ± 21 cm2 [p = 0.001] and 53 ± 21 cm2 vs. 30 ± 15 cm2 [p = 0.001], respectively) and epicardium (76 ± 28 cm2 vs. 51 ± 29 cm2 [p = 0.032] and 59 ± 25 cm2 vs. 37 ± 19 cm2 [p = 0.008]). In the multivariate analysis, MRI endocardial scar extension was the only independent predictor of VT recurrence (hazard ratio: 1.310 [per 10 cm2 ]; 95% confidence interval: 1.051 to 1.632; p = 0.034). Freedom from VT recurrence was higher in patients with small endocardial scars by MRI (